One area of climbing / bolting utility would be for folks learning to place bolts (or for old hands to reconfirm their practices). Place the bolt in some scrap rock & actually see if you're method results in something that is really trustworthy. (I.e. Do you overtorque? Do you undertorque? Did you really get the hole clean? Did you really make it the right size? etc. )

That particular company sell testers up to 495kN but thatīs a bit over the top for most climbing applications! As USNavy says, at least 40kN is needed to pull almost any decent bolt and there are plenty out there that get to the high 50īs or more, weīve seen over 100kN on a bolt pulling straight out! The biggest problem with the Hydrajaws and most other similar testers, apart from the cost, is the limited stroke. When you start really pulling the bolt and hanger distort and stretch and to pull it completely out you are going to need a stroke of 4 to 6" at the least. For on-site testing we use a 20 ton puller with a stroke of 6" and an initial load cell eye distance (from the bolt eye) of 6" which gives us enough pull (12" total) for our longer bolts. All this weighs about 30kg and is not the most convenient thing to use on a cliff!

There isnīt a whole lot of difference in the straight out pull strength (axial) to the radial for most bolts in most rock types and the axial test is normally the one performed as this would normally give the worst case scenario.

* Strength depends on the loading mode: either tension (pullout) or shear * Tensile strength is strongly affected by rock type, and depth of embedment * Shear strength is less affected by these * Both tensile and shear strengths are reduced by the proximity of another anchor, or to an edge, up to a certain critical distance, greater than this there is no effect * Anchors tend to fail in one of the following manners: rock/concrete breakage, bond failure (or expansion pullout), or anchor material fracture (metal breaks) * Selection of appropriate glue can allow the same or greater strength as the rock/concrete the anchor is placed in. Bonding is improved by roughening the anchor legs, either by grooves, knurling, or threads. This gives the glue something to key onto * The strength of anchors, in either shear or tension, is quite variable. Therefore an overall strength rating can only be gauged by performing a certain minimum number of tests, at least three, but ideally more

You don't want to pull a bolt to anywhere near its breaking strength because it weakens them.

15kn is more than strong enough for a bolt. Your body will break before the bolt pulls.

We usually test to 7.5kn.

If your questioning whether a particular bolt is safe or not, the only appropriate answer is to replace the bolt. And no 15 kN is not strong enough, that's why UIAA requires 25 kN for sheer. Its very possible to produce 15 kN on the top anchor on a fall straight into the belay station.

I use 1/2" Power-Bolts or more commonly, glue-in bolts with a failure strength of 40 kN. But that's irrelevant. No I promise you, your body will not break first. Do you think the UIAA pulled that 25 kN requirement out of their ass? They require bolts to hold 25 kN in sheer and 20 kN in tension because 20 kN is the approximate force the top anchor is subjected to with a factor 1.78 fall w/ 80 kg on a rope with an impact force of 12 kN with the pulley effect in play. Also the anchor must be robust enough to withstand big falls without deformation. If the anchor has a failure strength of 15 kN, repeated 10 kN loads can cause the anchor to fail as the anchor may bend with every load.

Thus there must be an additional margin of strength well beyond the maximum load the anchor will be subjected to on a regular basis. Thats the whole reason why the term "Safe Working Load" exists. SWL is generally 20% of the breaking strength of the product for non-critical applications and 1/15th the breaking load for life support applications. That additional margin exists to account for product deformation under serious loads, general wear, improper use, and many of the other situations that can cause a product to fail.

I use 1/2" Power-Bolts or more commonly, glue-in bolts with a failure strength of 40 kN. But that's irrelevant. No I promise you, your body will not break first. Do you think the UIAA pulled that 25 kN requirement out of their ass? They require bolts to hold 25 kN in sheer and 20 kN in tension because 20 kN is the approximate force the top anchor is subjected to with a factor 1.78 fall w/ 80 kg on a rope with an impact force of 12 kN with the pulley effect in play. Also the anchor must be robust enough to withstand big falls without deformation. If the anchor has a failure strength of 15 kN, repeated 10 kN loads will very likely cause the anchor to fail as the anchor will bend with every load. Thus there must be an additional margin of strength well beyond the maximum load the anchor will be subjected to on a regular basis.

I use 1/2" Power-Bolts or more commonly, glue-in bolts with a failure strength of 40 kN. But that's irrelevant. No I promise you, your body will not break first. Do you think the UIAA pulled that 25 kN requirement out of their ass? They require bolts to hold 25 kN in sheer and 20 kN in tension because 20 kN is the approximate force the top anchor is subjected to with a factor 1.78 fall w/ 80 kg on a rope with an impact force of 12 kN with the pulley effect in play. Also the anchor must be robust enough to withstand big falls without deformation. If the anchor has a failure strength of 15 kN, repeated 10 kN loads will very likely cause the anchor to fail as the anchor will bend with every load. Thus there must be an additional margin of strength well beyond the maximum load the anchor will be subjected to on a regular basis.

Its pointless to argue, UIAA requires 25 kN for a reason. An anchor with a failure strength of 15 kN will not meet EN or UIAA requirements and installing such is complete utter negligence. A standard good quality 3/8 bolt is capable of withstanding around 20 kN in sheer. Some can withstand close to 30 kN so there is no excuse to install substandard bolts. The UIAA and the Air Force have conducted extremely in-depth research regarding the application of serious force on the human body and they have found the maximum impact force a human body can sustain for a very short period of time with the spine aligned upright is 12 kN. Thats the reason why the UIAA requires their ropes have an impact force of 12 kN or lower. If the impact force on the climber side of the rope is 12 kN the impact force on the belayer side will be 6 - 8 kN and the force on the top anchor will be 18 - 20 kN. Once again, thats why they require biners to hold 20 kN along the major axis and bolts to hold 20 kN in tension and 25 in sheer. Thats also why they require slings to hold 22 kN and harnesses to hold 15 kN.

Using the UIAA testing standards as a reference is a good tool to help understand the maximum impact force involved in a worst case scenario fall. All of UIAA's certifications for free climbing equipment are based around a factor 1.78 fall with 80 kg and a rope with an impact force specification of 12 kN. All the requirements for harnesses, slings, ropes, carabiners and the related are based on this worst case scenario fall. So its been clearly proven that the maximum impact force the average healthy human can withstand with their spine aligned upright is 12 kN. Accordingly if the climber weighs 80 kg and takes a fall serious enough to produce 12 kN on his/ her side of the rope, the anchor will see close to 20 kN, thus a bolt that only holds 15 kN is insufficient.

Considering the max impact force on a rope, I certainly wouldn't want to generate 15kn, regardless of the strength of a bolt.

USnavy has a point though (maybe his first ever) that you do want your gear to be comfortably able to hold the rigors of climbing, not just barely be able to. If I have to take several whips on a bolt several hundred people have whipped on before, it's nice to know the bolt is stronger than it needs to be.

I have placed (by hand on lead) 4 bolts that were weaker than 15kn. They were 5/16 Powers with the stud replaced with a grade 8. We reckon that they would hold 12-14kn and since I'd whip off a stopper placed well all day, that would be cool. Now this is in the middle of nowhere, if I ever get back to send the thing, I will replace the bolts.

And just to plug an awesome company and source of info, Jim Titt, who posted earlier up this thread knows his stuff better than anyone out there. Here is a link to his site, http://www.bolt-products.com/index.htm thanks to him I'll be placing bolts rated at 102kn (assuming good rock, which I do not have) 200mm deep.

Construction fasteners are tested inside their working load which (depending on its intended use and the local codes) will be around 20% to 25% of if ultimate failure. Climbing bolts have no working load, only an ultimate failure load and any test lower than this is utterly pointless. The only satisfactory test for climbing bolts is sample destruction (failure) testing and this point is agreed on by all the responsible authorities involved. As USNavy says, a certain amount of extra strength is desirable to give a reasonable working life with safety as bolts are permanently installed and no records are kept of possible incidents.

While the figures USNavy gives are correct in themselves there are other factors which require that bolts (and other metal component in the system) are stronger than the simplistic 12kN impact would suggest is nescessary. In falls the instantaneous peak loads are much higher than the drop test results on soft goods would imply, these loads are of extremely short duration and in the rope, harness and body are of no concern but in the metal components the rate of strain can easily achieve levels where the material is weaker. This is particularly a problem with a number of aluminium alloys and some grades of titanium, though generally stainless steel is relatively insensible. For this reason it is generally considered desirable to allow for this at the design stage, most hard goods manufacturers perform dynamic tests on their products to obtain the relationship between dynamic loads and the standard quasi static tests.

The only correction to USNavyīs figures would be to point out that while the tests, as he says, refer to an 80kg mass, this actually represents a climber weight of approximately 100kg and is derived from research into real body comparisons to surrogate testing. If you want to know more about how the UIAA and Cenorm decide on how strong items of climbing equipment should be then a good start is to read "How strong does your climbing gear need to be?" which was the keynote paper at the BMC Technical conference in 2003 and is on the UIAA website. (Google is your friend).

And just to plug an awesome company and source of info, Jim Titt, who posted earlier up this thread knows his stuff better than anyone out there. Here is a link to his site, http://www.bolt-products.com/index.htm